Drugs cut return of breast cancer

More evidence that a new class of drugs can reduce the chances of breast cancer recurring in women who have been treated for it was made public yesterday.

Many women are given the "gold standard" drug tamoxifen for five years if their breast cancer has been found to be of the type that is stimulated by oestrogen in the body. Tamoxifen works by blocking the function of molecules known as oestrogen receptors in the body.

The new class of drugs, the aromatase inhibitors, kick in at an earlier stage, preventing the body from producing oestrogen. Results from several trials, the latest of them released yesterday, suggest there are advantages to taking an aromatase inhibitor after some years of tamoxifen.

Charles Coombes, director of the Cancer Research UK laboratories at Imperial College London, Hammersmith and Charing Cross hospitals, and leader of the latest trials on an aromatase inhibitor called exemestane, explained that the effects of tamoxifen can wear off in some patients.

"While tamoxifen can prevent recurrence in most patients, there are many who relapse within five years of diagnosis because breast cancer can become resistant to the drug. So we thought that switching from tamoxifen to an aromatase inhibitor - in this case exemestane - during a five-year course of hormone treatment could be beneficial.

"In a few cases, prolonged use of tamoxifen can also result in blood-clotting disorders and cancer of the uterus. By cutting use of the drug to two or three years we hoped to give patients benefit while minimising the risk of long-term side-effects."

By putting women on three years of tamoxifen followed by two years of exemestane, doctors hope they will retain one of the benefits of tamoxifen, which is the beneficial effect on woman's bone density not seen with the new drugs.

In all, 4,742 post-menopausal women from 37 countries including the UK took part in the latest trials between 1998 and 2003. All took tamoxifen for between two and three years. Half were then switched to exemestane. Researchers found the disease-free survival rate three years later was 92% in patients who switched to exemestane, compared with 87% for those who continued on tamoxifen.

Trials on two other aromatase inhibitors, letrozole, given after five years of tamoxifen, and anastrozole, given instead of tamoxifen, have also shown a reduction in breast cancer recurrence.

Delyth Morgan, the chief executive of Breakthrough Breast Cancer, said exemestane, like the other aromatase inhibitors, "offers new ways of reducing the risk of breast cancer returning. While this trial is extremely promising, the results are preliminary. The trial needs to continue before the long-term effectiveness and side effects are established."